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.. -*- rst -*-
.. highlightlang:: none
.. groonga-command
.. database: commands_column_rename
``column_rename``
=================
Summary
-------
``column_rename`` command renames a column.
It is a light operation. It just changes a relationship between name
and the column object. It doesn't copy column values.
It is a dangerous operation. You must stop all operations including
read operations while you run ``column_rename``. If the following case
is occurred, Groonga process may be crashed:
* Starts an operation (like ``select``) that accesses the column to
be renamed by the current column name. The current column name is
called as ``the old column name`` in the below because the column
name is renamed.
* Runs ``column_rename``. The ``select`` is still running.
* The ``select`` accesses the column to be renamed by the old column
name. But the ``select`` can't find the column by the old name
because the column has been renamed to the new column name. It may
crash the Groonga process.
Syntax
------
This command takes three parameters.
All parameters are required::
column_rename table name new_name
Usage
-----
Here is a simple example of ``column_rename`` command.
.. groonga-command
.. include:: ../../example/reference/commands/column_rename/column_rename.log
.. table_create Users TABLE_PAT_KEY ShortText
.. column_create Users score COLUMN_SCALAR Int32
.. load --table Users
.. [
.. {"_key": "Alice", "score": 2},
.. {"_key": "Bob", "score": 0},
.. {"_key": "Carlos", "score": -1}
.. ]
.. column_rename Users score point
.. column_list Users
.. select Users
Parameters
----------
This section describes parameters of ``column_rename``.
Required parameters
^^^^^^^^^^^^^^^^^^^
All parameters are required.
``table``
"""""""""
Specifies the name of table that has the column to be renamed.
``name``
""""""""
Specifies the column name to be renamed.
``new_name``
""""""""""""
Specifies the new column name.
Return value
------------
::
[HEADER, SUCCEEDED_OR_NOT]
``HEADER``
See :doc:`/reference/command/output_format` about ``HEADER``.
``SUCCEEDED_OR_NOT``
It is ``true`` on success, ``false`` otherwise.
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